Pipeline transport is the transportation of goods through a pipe. This form of transportation is crucial to shipment of products and the prompt and efficient provision of products consumers. Liquids and gases are the most common substances sent through a pipeline. FIG. 1 shows a schematic of the general operation of a pipeline. Pipeline networks are composed of several pieces of equipment that operate together to move products from location to location. The main elements of a pipeline system are shown in FIG. 1. The first component is the initial injections station 100. Known also as supply or inlet station, the initial injections station is the beginning of the system, where the product is injected into the line. Storage facilities, pumps or compressors are usually located at these locations. The compressor/pump stations 102 are pumps for liquid pipelines and compressors for gas pipelines, are located along the line to move the product through the pipeline. The location of these stations is defined by the topography of the terrain, the type of product being transported, or operational conditions of the network. The Partial delivery station 104 known also as an intermediate station allows the pipeline operator to deliver part of the product being transported. The Block valve stations 106 are the first line of protection for pipelines. With these valves the operator can isolate any segment of the line for maintenance work or isolate a rupture or leak. Block valve stations are usually located every 20 to 30 miles (48 km), depending on the type of pipeline. Even though it is not a design rule, it is a very usual practice in liquid pipelines. The location of these stations depends exclusively on the nature of the product being transported, the trajectory of the pipeline and/or the operational conditions of the line. The Regulator station is a special type of valve station, where the operator can release some of the pressure from the line. Regulators are usually located at the downhill side of a peak. Last, the final delivery station 108 known also as outlet stations or terminal this is where the product will be distributed to the consumer. It could be a tank terminal for liquid pipelines or a connection to a distribution network for gas pipelines.
FIG. 2 is an illustration of a pipeline system. As shown, when a pipeline is built, the construction project not only covers the civil work to lay the pipeline 200 and build the pump/compressor stations and control valves, it also has to cover all the work related to the installation of the field devices that will support remote operation. Field device instrumentation gathers data. The field instrumentation includes flow (O), pressure (P) and temperature (T) gauges/transmitters, and other devices to measure the relevant data required. These instruments are installed along the pipeline on some specific locations, such as injection or delivery stations, pump stations (liquid pipelines) or compressor stations (gas pipelines), and block valve stations 202. The information measured by these field instruments is then gathered in local Remote Terminal Units (RTU) 204 that transfer the field data to a central location 206 in real time using communication systems, such as satellite channels 208, microwave links, or cellular phone connections. Pipelines are controlled and operated remotely, from what is usually known as The Main Control Room 206. In this center, all the data related to field measurement is consolidated in one central database. The data is received from multiple RTUs along the pipeline. It is common to find RTUs installed at every station along the pipeline.
The SCADA system (supervisory control and data acquisition) is an industrial control system: a computer system monitoring and controlling a process. The SCADA is located at the Main Control Room 206 and receives all the field data and presents it to the pipeline operator through a set of screens or Human Machine Interface, showing the operational conditions of the pipeline. The operator can monitor the hydraulic conditions of the line, as well as send operational commands (open/close valves, turn on/off compressors or pumps, change set points, etc.) through the SCADA system to the field. To optimize and secure the operation of these assets, some pipeline companies are using what are called Advanced Pipeline Applications, which are software tools installed on top of the SCADA system, that provide extended functionality to perform leak detection, leak location, batch tracking (liquid lines), pig tracking, composition tracking, predictive modeling, look ahead modeling, operator training and more.
The primary component in a pipeline used to control the flow of substances through a pipeline is the valve. A valve is a mechanical device, which opens and closes in order to control the flow of materials, such as water, stream, oil, and gas chemicals, in flow lines such as pipes and vessels. Valves are used in a wide variety of familiar devices and many known tasks. For example, turning a dial on a gas stove varies the opening of a valve and regulates the flow of gas to the stove burner. The valve in an automobile tire allows air to enter but not to leave the tire. Valves in a steam radiator permit the air in the radiator to leave and the steam to take the place of air. In addition, valves may vary in size from a fraction of an inch to several feet, depending upon the diameter of the pipe or passageway. Valves are joined to a pipeline by threaded, flanged, or welded joints.
Some conventional valves consist of two main sections that form the valve housing/body: the bonnet section and the body section. The features of a conventional valve also include inlet and outlet openings to enable materials to flow through into, through and out of the valve. The valve also includes a restriction component (often referred to as a plug) that can be positioned in the area between the inlet and outlet opening to partially or totally restrict the flow of materials through the valve and thereby affect the flow rate and pressure of the materials. The fourth feature of the valve comprises an actuation mechanism to control the positioning of the restriction component between the two openings. Valve operators usually adjust the position of the restriction component through the actuation mechanism.
Valves fall into two broad types: linear and rotary. In a linear valve, the disc/plug lifts from the seat and moves in a direction that is perpendicular to the seat. By comparison, in a rotary valve such as a ball valve the disc rotates in the seat. A traditional type of linear valve called a gate valve. This valve has a stem and plug that moves in an up and down linear directions. A wheel connects to the stem. The operator rotates the wheel in one circular direction (usually clockwise) to lower the plug into the flowline. Rotating the wheel in the opposite circular direction will cause the stem to move upward and thereby raising the plug out of the flowline. The valve also contains a bonnet and a body that form the valve housing.
Control valves can be operated through various methods. The oldest and most basic method of operating a control valve is through manual control. With manual control an operator physically adjust the valve. A second form of valve control is with electronic controls that are manually operated. The operator uses an electronic device to adjust the valve instead of manually adjusting the valve. A third form of control is remote automatic control. Pipelines can have lengths of several thousands of miles. These pipelines contain control valves positioned at various locations in the pipeline. In rural areas, control valves may be approximately 25 miles apart. In more urban areas, pipelines may be approximately 5 miles apart. Because of the positions of the control valves, the optimum method to control valves is through remote automated control.
Currently, automated valve control systems exist. These control systems contain sensors that detect and transmit valve data and software programs that interpret the censored data and transmit commands that adjust and control the position of the valves as needed based on the interpreted data. These remote control valves are powered with battery power or have remote power stations in close proximity to the control valve. Although current valve control systems provide a means to regulate the flow of substances through a pipeline, the current methods and systems for powering the valves can be inefficient and unreliable. Valve control systems must to be able to function instantaneously even after being inactive for substantial periods of time. In addition, these systems must be able to properly function without the assistance or operation of human personnel. Further, the power needed to operate the valves must be sufficient at all times and must also be reliable.
Although valve control systems currently exist, there remains a need for a self-contain valve control system with an independent and sufficient power source and the capabilities to be internally operated in response to pipeline condition changes.